Recombination in Organic Bulk Heterojunction Solar Cells: Small Dependence of Interfacial Charge Transfer Kinetics on Fullerene Affinity
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- 作者：Antonio Guerrero ; Luis F. Marchesi ; Pablo P. Boix ; Juan Bisquert ; Germa Garcia-Belmonte
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2012
- 出版时间：May 17, 2012
- 年：2012
- 卷：3
- 期：10
- 页码：1386-1392
- 全文大小：307K
- 年卷期：v.3,no.10(May 17, 2012)
- ISSN：1948-7185
文摘
We investigate the causes for obtaining higher open-circuit voltage in solar cells that use a fullerene with a smaller electron affinity. Using impedance spectroscopy technique, we show that the change of fullerene LUMO energy has very little influence on the kinetic rate of charge transfer across the interface. In terms of the Marcus theory, large reorganization energy values govern the recombination kinetic rate, which is only slightly dependent on the fullerene LUMO energy, and also depends weakly on the energy location of recombining carriers within the broad density of states. Since the recombination rate is very similar in the different devices, we conclude that the larger open-circuit voltage is due to the larger donor HOMO/acceptor LUMO offset.